1. Field of the Invention
The invention relates generally to a vehicle seat that is mounted in a vehicle, for example, a car, and more specifically to a tilt-down vehicle seat in which a seat cushion moves downward as a seatback is tilted downward.
2. Description of the Related Art
In a tilt-down vehicle seat described in Japanese Patent Application Publication No. 2005-280501 (JP-A-2005-280501), as a seatback is tilted downward, a seat cushion moves downward. Thus, the seat is lowered. As a result, a space for baggage is obtained. A vehicle seat of this type usually includes a base member that is provided on a vehicle floor, a lower arm that is pivotally connected to a rear portion of the base member, a seatback that is pivotally connected to an upper portion of the lower arm via a reclining mechanism, a front link and a rear link that connect a seat cushion to the base member and that may pivot with respect to the base member, a connection link that is pivotally connected to a middle portion of the front link and the lower arm, and a lock mechanism that locks the lower arm to the base member. Therefore, when locking provided by the lock mechanism is cancelled and the seatback is tilted downward, the seatback and the lower arm are tilted down with respect to the base member, the lower arm pushes the connection link, the front link is tilted downward by the connection link, and the rear link is also tilted downward. Thus, the seat cushion moves downward in a substantially horizontal position.
French Patent Application Publication No. 2804072 describes a vehicle seat which includes a base member that is provided on a vehicle floor, a front seat cushion and a rear seat cushion which are separate members, a seatback that is pivotally connected to the base member via a reclining mechanism, at a position posterior to the rear seat cushion; a front link that connects a front end portion of the front seat cushion with the vehicle floor and that may pivot with respect to the vehicle floor; a guide mechanism that slidably supports a rear end portion of the front seat cushion and guides the rear end portion in such a manner that the rear end portion slides with respect to the base member, and an interlocking mechanism that causes the front seat cushion to move in accordance with the movement of the seatback.
The guide mechanism has a guide pin provided at the rear end portion of the front seat cushion, and an elongate guide groove which is formed in the base member and in which the guide pin is fitted. The link mechanism includes an arm that moves in accordance with the seatback, a first connection link, and a second connection link. The first connection link is pivotally connected to the second connection link at a portion near the guide pin, and the arm. The second connection link is pivotally connected to the first connection link and a lower portion of the seat cushion. Therefore, when the seatback is tilted downward, the first connection link pulls the second connection link and the second connection link pulls the rear end portion of the front seat cushion. Thus, the rear end portion of the front seat cushion is moved rearward and downward by the guide mechanism, and the front end portion of the front seat cushion is moved downward because the front link is tilted downward.
The paths, along which the front portion and the rear portion of the seat cushion described in JP-A-2005-280501 are moved, are set to arc-shaped paths because the paths along which the front link and the rear link pivot are arc-shaped. Therefore, the path along which the seat cushion is moved is not flexibly selected. Accordingly, when the seat cushion moves in accordance with the movement of the seatback, the seat cushion and the seatback may interfere with each other, which hinders a smooth operation of the seat. As a result, an operation load required to change the position of the seat may be increased. The connection structure described in French Patent Application Publication No. 2804072 includes two or more connection links. In addition, in order to set the pivot points of the connection links to desired positions, the connection links and the base member need to be formed in complicated shapes.